DisplayPort MST Support Is In The Works For Linux
Written by Michael Larabel in Hardware on 2 April 2014 at 10:37 AM EDT. 10 Comments
Hardware
David Airlie has begun hacking on DisplayPort Multi-Stream Transport handling for the open-source DRM/KMS graphics drivers.

Multi-Stream Transport (MST) is what allows daisy-chaining multiple DisplayPort displays off a single DisplayPort connector. Multi-Stream Transport was added to the DisplayPort 1.2 specification and can be achieved not only by daisy-chaining but also using a MST hub for having up to three connectors off a single DisplayPort connector.

DisplayPort MST is common right now among some 4K DisplayPort monitors that are technically two panels exposed side-by-side. It was also discovered that among newer Lenovo ThinkPad docks they are using one DisplayPort connector and then from the dock exposing VGA, HDMI, DVI, and DisplayPort connections. This is what's led David Airlie at Red Hat to begun hacking on the MST handling for the DRM/KMS drivers.

Right now trying to use MST will just yield a single-stream and the same image being broadcast across all displays. So far David has brought up the first step of encoding the topolgy discovery message and receiving responses from the dock. However, there's much more work ahead. Besides the Lenovo dock, he will also be playing aorund with a DP MST hub for AMD and NVIDIA DRM graphics drivers with the ThinkPad T440s using Intel graphics. More details on this open-source DisplayPort MST work can be found via David's blog. The only downside to this work is that it's taking him away from Virgil3D development.
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Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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